Labor senator Penny Wong tweeted this picture of daughters Alexandra and Hannah after her partner Sophie Allouache gave birth to their second child on Good Friday in Adelaide

The couple used the same sperm donor who helped them become parents to three-year-old Alexandra

'Sophie and I are delighted to announce the arrival of Hannah, a sister to Alexandra,' she said.

'Everyone is doing well.'

It is the second child for the long-term couple who welcomed their eldest daughter Alexandra in 2011.

Hannah was conceived through IVF by the same man who helped them become parents to Alex.

The couple announced they were having another child in December last year in an interview with The Advertiser.

Their three-year-old helped spill the beans.

It is the second child for the long-term couple who welcomed their eldest daughter Alexandra (pictured) in 2011

Ms Wong shared news of her second daughter's brith with her 100,000 Twitter followers on Tuesday morning

'Like all families we had to think about whether we tell the toddler because she's notorious - she doesn't know what a secret is,' she told the newspaper at the time.

'But we decided to tell her because we thought it was important she knew.

'Which was fine except at the Labor convention she sat reading The Gruffalo to a baby over and over again... I came over and asked how it was going and a friend said 'it's all really good but she's just told everyone Mummy's got a baby in her tummy'.'